The Dow Jones industrial average was down 22 points, or 0.2 per cent, at 14,556 at noon Monday.
The Standard & Poor's 500 index dropped seven points, or 0.5 per cent, to 1,562.
The Nasdaq composite fell 20 points, or 0.6 per cent, to 3,246.
U.S. manufacturing kept growing for a fourth straight month in March, but at a slower rate, according to the Institute for Supply Management.
The S&P 500 closed at an all-time high last week and is up 10 per cent for the year. The index has recaptured all its losses from the financial crisis and the Great Recession.
EBay rose after predicting more growth in its e-commerce and online payments business.